Dr Jens Zimmermann said it would be in Britain's interest to do this, adding that he believed the German government wouldn't block it.

He said that any agreement with Britain following a withdrawal would have to be backed by all EU member states.

But he said there may be the possibility of a "bilateral solution" for Ireland, with the other EU countries acknowledging the special relationship between Ireland and Britain.

"I think it would be in the interests of the UK to find a quick solution, especially concerning the relationship to Ireland, and I think Germany wouldn't be in opposition to that," Zimmermann told the Sunday Independent. "But it's complicated."

Ireland is expected to be the EU country worst hit by a possible British withdrawal from the EU, given its close economic, political and societal links. The impact on the peace process, the border with the North and trade between the UK and Ireland are the main issues of concern for the Irish Government.

Zimmermann said the negotiations following a possible vote to withdraw would be very difficult to complete within the two-year period, given their complexity.

"I think there might be a bilateral solution for Ireland in that situation and I think the other European member states would acknowledge that there is a special relationship between Ireland and the UK. But nobody knows," he added. Zimmerman also said he believed British Prime Minister David Cameron would have to resign if the British vote to pull out, or "the Tories would force him out".

Meanwhile, an international expert in regional and urban economics has warned that a Brexit could lead to the break-up of the EU.

"You've got a lot of nationalist tensions in most of the continent, particularly in Hungary, Poland, there's the rise of Le Pen, Pegida in Germany. You've still got the negotiations going on in Greece about the Eurozone crisis. Most of the discussion about Brexit is focused on the UK economy but there's a big feedback loop... the whole of the EU economy could be damaged," said Dr Leslie Budd, who is also an economic advisor to the Enterprise, Trade and Investment committee of the Northern Ireland Assembly.

"Given those political tensions, you could start to see some sort of fracture and break-up."